Prince Williamdropped out of a ceremony to honor his godfather King Constantine of Greece due to a personal matter, Kensington Palace says.

The Prince of Wales, 41, pulled out of the service of Thanksgiving at St. George’s Chapel in Windsor Castle on Tuesday. The personal matter is not related to the health of his father,King Charles, who wasrecently diagnosed with cancer, PEOPLE understands.

Prince William, who was set to do a reading at the service according to the order of service, was due to attend without his wifeKate Middleton, 42, who is recovering from herrecent abdominal surgeryat home in Adelaide Cottage on the Windsor estate. While the palace didn’t indicate whether William’s absence was due to Kate’s recovery, a palace source tells PEOPLE she “continues to be doing well.”

Prince William in London on September 13, 2023.JUSTIN TALLIS/POOL/AFP via Getty Images

Prince William, Prince of Wales talks with workers from across the construction industry before visiting a construction site in north-west London on September 13, 2023

JUSTIN TALLIS/POOL/AFP via Getty Images

Constantine, who was the last King of Greece,died in January 2023 at age 82and among the congregation for the service was King Constantine’s widow, Queen Anne-Marie, and their son Crown Prince Pavlos with his wife, Crown Princess Marie-Chantal. Prince William informed the late King’s family he was unable to attend ahead of the event.

Prince William, Prince of Wales and Catherine, Princess of Wales attend a service to commemorate the life of Her Late Majesty Queen Elizabeth II at St Davids Cathedral on September 8, 2023 in St Davids, Wales.

Queen Camillaformally led the British royal family, stepping in for her husband,King Charles, who isundergoing cancer treatmentand has canceled most public-facing duties.

Queen Camilla arrives at the thanksgiving service on Tuesday, February 27, 2024.ANDREW MATTHEWS/POOL/AFP via Getty Images

Queen Camilla arrives to attend a thanksgiving service for the life of King Constantine of the Hellenes, at St George’s Chapel at Windsor Castle

ANDREW MATTHEWS/POOL/AFP via Getty Images

The big turnout of royals also included their eldest daughterPrincess Beatriceand her husbandEdoardo Mapelli Mozzi.

Prince Andrew and Sarah Ferguson, the Duke and Duchess of York arrive at the service at St. Geroge’s Chapel, Windsor Castle.CHRIS JACKSON/POOL/AFP via Getty Images

Prince Andrew, Duke of York and Sarah, Duchess of York arrive to attend a thanksgiving service for the life of King Constantine of the Hellenes, at St George’s Chapel at Windsor Castle

CHRIS JACKSON/POOL/AFP via Getty Images

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The guests at the Windsor Castle service also included Princess Alexandra, the Duke and Duchess of Gloucester, Prince and Princess Michael of Kent, the Duke of Kent and Princess Margaret’s daughter Lady Sarah Chatto.

Outside the British royal family, King Felipe and Queen Letizia of Spain as well as former King Juan Carlos and Queen Sofia of Spain, Princess Benedikte of Denmark, Queen Noor of Jordan and Prince Constantijn of the Netherlands.

Zara Tindall, Mike Tindall and Anne, Princess Royal attend the Thanksgiving Service for King Constantine of the Hellenes at St George’s Chapel

Chris Jackson/Getty Images

The links between the British and Greek royal families are strong, and Constantine was a close friend of both King Charles and his late mother,Queen Elizabeth. Her husband,Prince Philip, was born in Crete and was a first cousin of King Constantine’s father, King Paul I. Prince William is himself godfather to one of Prince Pavlos' children.

Constantine acceded to the throne at the age of 23 in 1964, reported the Associated Press. By then, he was already an Olympic gold medalist in sailing.

The late King Constantine of Greece.Jeff Overs/BBC News & Current Affairs via Getty

Constantine II (former Greek King) on BBC Breakfast with Frost, Sunday 10th April 2005. (Photo by Jeff Overs/BBC News & Current Affairs via Getty Images)

After suffering fromchronic heart and mobility problems, his condition worsened and he was hospitalized last January, according to Reuters. He died in Athens, the city of his birth, on January 10, 2023.

Prince William did not attend King Constantine’s funerallast year. Instead, he asked his relative Lady Gabriella Windsor to represent him. It was a poignant choice as Lady Gabriella is the daughter of Prince Michael of Kent, a first cousin to the lateQueen Elizabeth, to whom Constantine was a close friend. Gabriella and William also share another link: Constantine was a godfather to them both.

At the funeral,Princess Annestood in for her brother King Charles at the solemn ceremony in Athens.

Queen Anne Marie of Greece and Crown Prince Pavlos of Greece attend the funeral of Former King Constantine II of Greece.Patrick van Katwijk/Getty Images

Queen Anne Marie of Greece and Crown Prince Pavlos of Greece attend the funeral of Former King Constantine II of Greece

It is customary for senior royals in Britain to send relatives or close friends and aides to funerals on their behalf. The late Queen Elizabeth only rarely attended funerals. King Charles appears to be following the same custom and sending a family member instead.

Other royals from around the world in attendance at the funeral includedPrince Albertof Monaco, King Felipe and Queen Letizia of Spain, Queen Margrethe of Denmark (who was the late monarch’s sister-in-law), King Philippe and Queen Mathilde of Belgium, King Willem-Alexander and Queen Maxima of the Netherlands and Crown Prince Haakon of Norway and Crown Princess Mette-Marit of Norway.

source: people.com